Mass spectral studies

The major component of the oil extracted from bell peppers has been shown, initially on the basis of mass spectral studies but subsequently by total synthesis, to be 2-methoxy-3-... 

Echinomycin (131) has been shown to be an antitumor agent and to have antiviral and antibacterial properties. Its structure elucidation represents a triumph for and mass spectral studies (75JA2497). It has been demonstrated that echinomycin functions by inhibiting RNA synthesis in organisms such as Staphylococcus aureus. Echinomycin, levomycin and actinoleutin are members of the quinoxaline-peptide antibiotic family and all contain one or more quinoxaline rings (67MI21402). 

An interesting mass spectral study of 17 mono- and dflialogenoquinoxahnes, some bearing methyl groups, has been reported the X-ray crystallographic structure of hexachloroquinoxaline has been measured. ... 

Chemical-ionization mass-spectral studies for typical per-O-acetylglyco-pyranosyl and -furanosyl fluorides have been reported. 

Carlier, J. P. Sellier, N. Gas chromatographic-mass spectral studies after methyla-tion of metabolites produced by some anaerobic bacteria in spent media. J. Chro-matogr. 1989, 493, 257-273. 

Mass spectral studies, including low voltage techniques and accurate mass measurements, have been reported by Hoffman (40) on tetracycline and eight related compounds. As a result of good spectral correlations among these compounds, the major fragmentation processes are discussed in terms of two compounds in the series 5a,6-anhydrotetracycline and... 

Sulfoxide adducts of chromium, molybdenum, and tungsten carbonyls have been studied as catalysts for the polymerization of monomers such as vinyl chloride (248). Simple adducts of the type [M(CO)5(Me2SO)] may be prepared by carbonyl displacement from the corresponding hexacarbonyl. Photochemical reactions are frequently necessary to cause carbonyl displacement in this manner, many carbonyl complexes of higher sulfoxides have been prepared (255, 256). Infrared (257) and mass spectral studies (154) of these complexes have appeared, and infrared data suggest that S-bonding may occur in Cr(0) sulfoxide complexes, although definitive studies have not been reported. 

As in the case of chromium and tungsten, manganese carbonyl adducts of Me2SO have been used as catalysts for the polymerization of vinyl chloride (248). Preparative studies have allowed the isolation of complexes of the type [MnCCpHjMeXCOlXRaSO)] [RjSO = (CH2)4SO, (CH20)2S0 see ref. 255], and infrared (257) and mass spectral studies (154, 275) have appeared on these and related systems. 

The formation of gaseous organic cations under electron bombardment of alkanes, haloalkanes and other precursors has been widely investigated in mass spectral studies (Field and Franklin, 1957 McLafiFerty, 1963). 

Ardanaz, C.E. Guidugli, F.H. Calais, C.A.N. Joseph-Nadian, P. Mass Spectral Studies of Medioxynaphdioflavones. Rapid Common. Mass Spectrom. 1999, 13, 2071-2079. 

Guigugli, F.H. Kavka, J. Garibay, M.E. Santillan, R.L. Joseph-Nathan, P. Mass Spectral Studies of Naphthoflavones. Org. Mass Spectrom. 1987, 22, 479-485. 

Gillies, C. W., R. P. Lattimer, and R. L. Kuczkowski. Microwave and mass spectral studies of the ozonolyses of ethylene, propylene, and cu- and mm5-2-butene with added oxygen-18 formaldehyde and acetaldehyde. J. Amer. Chem. Soc. % 1536-1542, 1974. 

The various tautomers and rotamers of alloxan have been examined in detail by the MNDO method and it is predicted that the keto form is most important in the gas phase, although in solution the monohydroxy forms are also thought to contribute. A mass spectral study has been used to investigate the enol-keto tautomeric equilibria of a series of substituted salicylaldehyde and 2-hydroxynaphthaldehyde Schiff bases. In neutral, ethanolic solutions, the cis- and trans-tm forms of 4,5-dimethyl-2-(2 -hydroxyphenyl)imidazoles (393) and (394) have been found to exist in equilibrium in the ground state. However, in neutral aqueous solutions, the trans-eao and keto forms (394) and (395) were the only species detected. Deuterium isotope effects on... 

The experiments were done at a collision energy of 2.9 eV, and it was found that the ability to distinguish quadricyclane from norbornadiene is lost for energies above 5 eV, where conventional tandem mass spectrometers operate. As expected from this result, previous mass spectral studies of C7H8 have been unable to distinguish quadricyclane and norbornadiene [18-22]. 

Osmiumfvi).—The i.r. spectrum of [OsOCl ] has been recorded in the gas and liquid phases, and in solution. While the exact geometry could not be deduced, evidence was obtained for facile co-ordination of acetone or ether to the species in inert solvents. A mass spectral study of this complex reveals a complex fragmentation pattern, including the previously unknown [OsOClj] species. ... 

Mass spectroscopic studies of organometallic compounds are almost as old as the field of mass spectrometry nickel tetracarbonyl was studied by J. J. Thomson (/) and Aston (2,3) in their work on the isotope ratios of nickel. Following this early flurry of specialized interest, however, inorganic and organometallic mass spectral studies were... 

The methods used for the isolation and derlvatization of the metabolites as well as the results from the detailed mass spectral studies presented in the original manuscripts (, 7) should have broad application in studies dealing with GSH conjugates of pesticides in plants. 

Mass spectral studies can distinguish between the N(4) and NH2 substitution of 3-aminotriazole in compounds (17) and (18) <88JHC565>. In (17) the base peak is at m/e 220, whereas this fragment is very small in (18), the base peak being at m/e 84. 

All the well-characterized 1,2,3-triazine derivatives are stable, high-melting solids. The 4,5,6-triaryl derivatives show UV maxima in the range 259-286 nm (log e = 4.09-4.42), 4,5-diphenyl-1,2,3-triazine has Amai at 251 nm, while the 4,5,6-trimethyl derivative shows two maxima at 217 nm (log e — 3.63) and 278 nm (log e = 2.79). Mass spectral studies indicate that fragmentation takes place in an identical fasMon to that observed during photochemical decomposition, i.e., with production of acetylenes, nitriles, and nitrogen. ... 

Much of the subsequent interest in these reactions was centered on the question of whether highly reactive intermediates such as 146 are generated during decomposition. High resolution mass spectral studies clearly reveal that for 10 loss of nitrogen and formation of species equivalent to 146 is one of the preferred fragmentation pathways (see Section II, D, 6), and it was tacitly assumed for some time that thermal... 

First, comparing the short Li—Li distances observed in all of these systems with twice the covalent radius of lithium, we find that appreciable interaction could occur. Further support for Li—Li interaction is provided by the observed mass spectral studies reviewed by Berkowitz (77), and certainly support comes from most of the theoretical calcula-... 

Isatin has been reported to fragment predominantly by successive loss of CO, HCN, and CO from the molecular ion on electron impact, and also by consecutive loss of two molecules of CO from the molecular ion followed by loss of HCN.236 Use of 3-13C-labeled isatin shows that the initial loss of CO occurs entirely from the 2-position.237 Mass spectral studies have also been carried out on a variety of derivatives of isatin.236-241... 

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